Current research findings on calcium-silicate unit production technology

摘要

Calcium-silicate (CS) units are made from the starting materials sand, lime and water. The raw materials are proportioned by weight, intensively mixed together and fed into reactors on a conveying system. Within the reactor, quicklime is quenched under water consumption to obtain hydrated lime. The green units are then hardened under steam pressure at temperatures of the order of 200 °C for about four to eight hours, depending on the product's geometry. The hot, steamy atmosphere dissolves silica from the quartz-sand grains, and the silica forms crystalline CSH phases with the hydrated lime, thereby firmly interlocking the grains of sand. After hardening and cooling, the calcium-silicate units are ready for use. The development of temperature-stable CSH reaction accelerators for industrial applications has made it possible to speed up the reactions that take place between the aggregates and the lime binder during autoclaving of green calcium-silicate units. Such CSH-phase reaction accelerators can be injected directly into the production process. Since only a relatively small amount of CSH phases is required (e.g., 1 m% in relation to the lime dose), the cost incurred for the CSH phases, which are relatively easy to produce anyway, is quite limited and quickly compensated, particularly considering the rising cost of energy. Hence, the amount of energy consumed during to the autoclave holding phase can be reduced with no detriment to the quality of the calcium-silicate unit products. Reducing fuel consumption not only reduces the relevant costs, but also contributes to climate protection by reducing CO_2 emissions accordingly [1, 2].